Infectious mononucleosis

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

Evidence last reviewed: 5 Jul 2026

Topic last updated: 24 Jul 2026

Infectious mononucleosis (IM) is characterized by the classic triad of fever, pharyngitis, and lymphadenopathy, along with atypical lymphocytosis. It is often subclinical in young children.

Caused by infection with Epstein-Barr virus (EBV) in up to 90% of cases. Positive serologic test for antibodies against EBV is usually diagnostic.

Rare but potentially life-threatening complications include severe upper airway obstruction, splenic rupture, fulminant hepatitis, encephalitis, severe thrombocytopenia, and hemolytic anemia.

Treatment is usually symptomatic.

Definition

IM, also known as glandular fever, is a clinical syndrome most commonly caused by EBV infection in up to 90% of cases.[1][2][3] Other causes are much less common. The diagnosis "IM" is primarily used when the syndrome is caused by infection with EBV; "mononucleosis syndrome" should be used when the syndrome is caused by a non-EBV etiology. This topic focuses on IM caused by infection with EBV.

IM typically manifests in adolescents and young adults as a febrile illness with sore throat and enlarged lymph nodes. The disease is generally mild in children, but more severe in adults. Resolution of the acute illness is usually followed by a lifelong latent infection, with over 90% of the adult population infected worldwide.[4]

History and exam

Key diagnostic factors

fever
pharyngitis
cervical or generalized lymphadenopathy
malaise

Full details

Other diagnostic factors

myalgia
splenomegaly
rash
signs of hepatitis (hepatomegaly, jaundice)

Full details

Risk factors

kissing
sexual behavior

Full details

Diagnostic tests

1st tests to order

CBC
Epstein-Barr virus (EBV)-specific antibodies
LFTs

Full details

Tests to avoid

serum Monospot for EBV infection

Full details

Tests to consider

real-time polymerase chain reaction (PCR)
CT of abdomen

Full details

Treatment algorithm

ACUTE

all patients

Contributors

Authors

George Turabelidze, MD, PhD

Medical Epidemiologist

Missouri Department of Health and Senior Services

Adjunct Assistant Professor of Clinical Pediatrics

Washington University School of Medicine

St Louis, MO

Disclosures

GT declares that he has no competing interests.

Peer reviewers

Ben Z. Katz , MD

Professor of Pediatrics

Northwestern University

Feinberg School of Medicine

Attending Physician

Division of Infectious Diseases

Ann & Robert H Lurie Children’s Hospital of Chicago

Chicago, IL

Disclosures

BZK declares that he has no competing interests.

Linda Kalilani, MBBS, MPhil, PhD

Epidemiologist

College of Medicine

University of Malawi

Zomba

Malawi

Disclosures

LK declares that she has no competing interests.

Peer reviewer acknowledgements

BMJ Best Practice topics are updated on a rolling basis in line with developments in evidence and guidance. The peer reviewers listed here have reviewed the content at least once during the history of the topic.

Disclosures

Peer reviewer affiliations and disclosures pertain to the time of the review.

References

Our in-house evidence and editorial teams collaborate with international expert contributors and peer reviewers to ensure that we provide access to the most clinically relevant information possible.

Key articles

Ganzel TM, Goldman JL, Padhya TA. Otolaryngologic clinical patterns in pediatric infectious mononucleosis. Am J Otolaryngol. 1996 Nov-Dec;17(6):397-400. Abstract

De Paor M, O'Brien K, Fahey T, et al. Antiviral agents for infectious mononucleosis (glandular fever). Cochrane Database Syst Rev. 2016 Dec 8;(12):CD011487.Full text Abstract

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.

Differentials
- Group A streptococcal pharyngitis
- Scarlet fever
- Hepatitis A
More Differentials
Guidelines
- Laboratory testing for Epstein-Barr virus (EBV)
- Clinical overview of Epstein-Barr virus (EBV)
More Guidelines
Patient information
Glandular fever (infectious mononucleosis)
More Patient information
Videos
Venepuncture and phlebotomy: animated demonstration
Peripheral intravascular catheter: animated demonstration
More videos
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Infectious mononucleosis

Summary

Definition

History and exam

Key diagnostic factors

Other diagnostic factors

Risk factors

Diagnostic tests

1st tests to order

Tests to avoid

Tests to consider

Treatment algorithm

all patients

Contributors

Authors

George Turabelidze, MD, PhD

Disclosures

Peer reviewers

Ben Z. Katz , MD

Disclosures

Linda Kalilani, MBBS, MPhil, PhD

Disclosures

Peer reviewer acknowledgements

Disclosures

References

Key articles

Reference articles

A full list of sources referenced in this topic is available to users with access to all of BMJ Best Practice.

Differentials

Guidelines

Patient information

Videos

Log in or subscribe to access all of BMJ Best Practice

Log in or subscribe to access all of BMJ Best Practice

Log in to access all of BMJ Best Practice